damn brotha you shoulda started flowering them when they were about 2ft or so, they usually double to triple in size during flower... but, you didn't know that so you can start bending the tops down toward the ground gradually, this should get u by for now... next time induce flowering when plants are rougly half the size you want when finished... no harm done, just bend the top over slightly and tie with twine or something, not tite but secure, then in a couple days bend a little more and retie... GL, and try and indica strain next time, they're much better for an indoor grow...